1. Field of the Invention
The present invention relates to a grease gun, and more particularly to a grease gun having an automatic continuous feeding device.
2. Description of the Related Art
A conventional pneumatic feeding type grease gun in accordance with the prior art shown in FIG. 1 comprises a gun body 2, a piston 21 mounted in the gun body 2, a spring 22 mounted in the gun body 2 for pushing the piston 21, and a plunger 23 mounted on the front end of the spring 22, so that the plunger 2 may be moved in the barrel 20. A container 24 is mounted on the gun body 2. A piston 26 is mounted in the container 24, and is pushed by a spring 25, so that the grease contained in the container 24 may be pushed to enter the barrel 20, and may then be pushed outward by the plunger 23. The gun body 2 has a handgrip 27 provided with an air inlet conduit 28 connected to the piston 21. A switch valve 29 is mounted on the air inlet conduit 28, and may be pressed by a trigger 291, so that the switch valve 29 may be opened or closed.
Before operation, the grease contained in the container 24 may be pushed by the piston 26 to enter the barrel 20. When the trigger 291 is pressed, the switch valve 29 is opened, whereby air of a high pressure may enter the gun body 2 through the air inlet conduit 28, to push the piston 21 which pushes the plunger 23 which may push the grease in the barrel 20 outward, thereby ejecting the grease outward. When the force on the trigger 291 is removed, the switch valve 29 is closed, whereby the air inlet conduit 28 is closed, and the air of a high pressure is released, so that the piston 21 is returned to its original position by pushing of the spring 22. Thus, the piston 21 may be successively moved forward and backward by pressing the trigger 291 repeatedly, so that the grease in the container 24 may be pushed outward intermittently.
However, the user has to press the trigger 291 successively so as to push the grease outward continuously, thereby causing inconvenience to the user in operation.
The present invention has arisen to mitigate and/or obviate the disadvantage of the conventional pneumatic feeding type grease gun.
The primary objective of the present invention is to provide a grease gun having an automatic continuous feeding device, wherein the piston may be moved reciprocally and automatically, such that the grease may be ejected outward continuously, without having to compress and loosen the trigger repeatedly, thereby facilitating the user operating the grease gun.
In accordance with the present invention, there is provided a grease gun having an automatic continuous feeding device, comprising:
a gun body formed with a piston chamber, a piston mounted in the piston chamber, a spring mounted in a front side of the piston chamber for pushing the piston, a barrel chamber formed in a front end of the gun body, and communicated between the front side of the piston chamber and an ambient environment, a plunger slidably mounted in the barrel chamber and having a distal end secured to a front end of the piston, a container secured to the front end of the gun body, and communicated with the barrel chamber, the gun body having a handgrip provided with an air inlet conduit connected to a rear side of the piston chamber, a switch valve mounted on the air inlet conduit, a trigger pivotally mounted on the gun body, and rested on a distal end of the switch valve; wherein:
the piston has two ends whose outer peripheries are provided with two sealing washers, so that the piston divides the piston chamber into a front side and a rear side, the piston has an outer periphery having a mediate portion formed with a recessed portion, the piston has an inner portion formed with a valve chamber, the piston is formed with a through hole that is communicated between the recessed portion and the valve chamber, a balance valve is mounted in the valve chamber, and has a first end provided With a piston portion mounted in the valve chamber and a second end provided with a valve portion that may seal a valve port of the valve chamber, a conduit is formed in the piston, and may connect the two sides of the piston chamber after the valve port of the valve chamber is opened, the piston chamber has a predetermined position provided with an air guide groove, whereby when the piston is moved in the piston chamber to the predetermined position of the piston chamber, one of the two sealing washers on the piston may align with the air guide groove, and an air drain hole is formed in the front end of the gun body, and is communicated between the front side of the piston chamber and an ambient environment; and wherein:
when the sealing washer at the rear end of the piston aligns with the air guide groove, a gap is formed between the outer wall of the piston and the inner wall of the piston chamber, so that air of a high pressure may enter the recessed portion of the piston through the air guide groove, and may enter the valve chamber in the piston through the through hole to push the balance valve in the valve chamber to move outward, so as to move the valve portion of the balance valve outward, thereby opening the valve port of the valve chamber, so that the front side and the rear side of the piston chamber at the two sides of the piston may communicate with each other through the valve chamber and the conduit;
the air of a high pressure in the rear side of the piston chamber may be drained outward to the ambient environment through the air drain hole, so that the pressure in the two sides of the piston chamber may be balanced, whereby the pushing force on the piston may be released, so that the piston may be pushed by the spring to move backward;
when the piston is moved backward to the rear side of the piston chamber, the valve portion of the balance valve hits the wall of the rear side of the piston chamber, thereby returning the balance valve to its original position, so that the valve portion of the balance valve may close the valve port of the valve chamber, and so that the air of a high pressure entering the rear side of the piston chamber through the air inlet conduit may push the piston to move forward again.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.